This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines are used to generate considerable levels of power for prolonged periods of time on a dependable basis. Many such engine assemblies employ a boosting device, such as an exhaust gas turbine driven turbocharger, to compress the airflow before it enters the intake manifold of the engine in order to increase power and efficiency.
Specifically, a turbocharger utilizes a centrifugal gas compressor that forces more air and, thus, more oxygen into the combustion chambers of the engine than is otherwise achievable with ambient atmospheric pressure. The additional mass of oxygen-containing air that is forced into the engine improves the engine's volumetric efficiency, allowing it to burn more fuel in a given cycle, and thereby produce more power.
A typical turbocharger employs a central shaft that is supported by one or more bearings and transmits rotational motion between an exhaust-driven turbine wheel and an air compressor wheel. Both the turbine and compressor wheels are fixed to the shaft, which in combination with various bearing components constitute the turbocharger's rotating assembly.
Sub synchronous frequency vibration noise can be a concern in a turbocharger. The semi-floating or fully floating bearing according to the principles of the present disclosure is designed to minimize sub synchronous vibration. In conventional bearings as shown in FIG. 4, the bearing 1 includes a pair of inner bearing surfaces 2 that engage the turbocharger shaft 3 and a pair of outer bearing surfaces 4 that contact the turbocharger housing. The inner bearing surfaces 2 of the conventional bearing 1 have an axial dimension DI that is smaller than an axial dimension DO of the pair of outer bearing surfaces 4.
However, it is a discovery of the present application that a reduced outer bearing surface axial dimension relative to the inner bearing surface axial dimension can decrease sub-synchronous frequency vibrations. Accordingly, the present disclosure provides a turbocharger including a housing and a rotary assembly disposed within the housing and including a turbine wheel and a compressor wheel attached to one another by a shaft. A bearing is disposed in the housing and rotatably supports the shaft. The bearing includes a pair of inner bearing surfaces that engage opposite ends of the shaft and a pair of outer bearing surfaces that engage the housing. The pair of inner bearing surfaces have a first axial dimension and the pair of outer bearing surfaces have a second axial dimension that is smaller than the first axial dimension.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.